How to remove file extension from string using JavaScript?
Many web applications allow users to upload files. Additionally, it displays the file content and file name after trimming the file extension.
In addition, sometimes we need to store the file content into the database with the file name without extension as a key. Therefore, various use cases require us to use the filename of the uploaded file, without the extension.
Here we will learn various ways to remove file extensions from strings using JavaScript.
Use array.split(), array.pop() and array.join() methods
Each file name includes the file extension after the last dot in the file name. So, we can split the file name by using "." as delimiter. After that we can use array.pop() method to remove the last element and concatenate the array elements again to get only the file name.
grammar
Users can use the array.split(), array.pop() and array.join() methods according to the following syntax.
let split = fileName.split('.');
split.pop();
let finalName = split.join(".");
algorithm
Step 1 – Get the file name of the uploaded file.
Step 2 – Split the file name by using a dot (.) as a separator.
Step 3 – Remove the extension from the array using the pop() method.
Step 4 – Use the join() method to join the split arrays without file extension.
Step 5 – The FinalName variable contains the file name with the extension trimmed.
Example 1
In the example below, we create a user input that allows the user to upload files in any format. Whenever a user uploads any file, it gets the file name using the name attribute and trims the file extension by executing the above algorithm.
In the output, the user can see the filename with or without extension.
<html>
<body>
<h2>Using the <i> array.split(), array.join(), and array.pop() </i> methods to remove the file extension from the string in JavaScript. </h2>
<div id = "output"></div> <br>
<input type = "file" onchange = "ShowFilename(this)">
<script>
let output = document.getElementById("output");
function ShowFilename(event) {
// get uploaded file name
let fileName = event.files[0].name;
output.innerHTML += "The original file name is " + fileName + "<br/>";
// split the file name
let split = fileName.split('.');
// remove the last element of the array
split.pop();
// join array again
let finalName = split.join(".");
output.innerHTML += "The file name after trimming the extension is " + finalName + "<br/>";
}
</script>
</body>
</html>
Use regular expressions
We can use regular expression search patterns to find file extensions in filename strings. Afterwards, we can use the string.replace() method to replace the file extension with an empty string.
grammar
Users can use regular expressions and replacement methods according to the following syntax to remove file extensions in strings.
let regex = new RegExp(/\.[^/.]+$/) let fileName = original.replace(regex, "");
We used the RegExp() constructor in the above syntax to create regular expressions.
Regular expression explanation
\. – Represents a string starting with the “.” character.
[^/.] - Indicates that the string contains at least one character other than "."
$ - Represents the end of the string.
The entire regular expression looks for patterns that contain a dot at the beginning, and then looks for characters other than the dot character before the end of the string.
Example 2
The following example takes the filename as a string with the ".html" extension in the original variable. When the user presses the button, we call the removeExtension() function.
In the removeExtension() function, we create the regular expression as above and store it in the regex variable. After that, we use the Replace() method to replace the same pattern (e.g. regular expression) with an empty string to remove the file extension from the filename string.
<html>
<body>
<h2>Using the <i> Regular expression </i> to remove the file extension from the string in JavaScript </h2>
<div id = "output"></div> <br>
<button onclick = "removeExtension()"> Remove extension </button>
<script>
let output = document.getElementById("output");
let original = "file.html"
output.innerHTML += "The original file name is " + original + "<br/>";
function removeExtension() {
let regex = new RegExp(/\.[^/.]+$/)
let fileName = original.replace(regex, "");
output.innerHTML += "The file name after trimming the extension is " + fileName + "<br/>";
}
</script>
</body>
</html>
Use substring() and lastIndexOf() methods
We can use the lastIndexOf() method to find the last index of the "." character in the file name, because we need to delete the entire string after the last dot representing the file extension.
The substring() method allows the user to get a substring using the start and end index. We can get the substring from the 0th index to the last ‘.’ character index.
grammar
Users can use the substring and lastIndexOf() methods according to the following syntax to remove the file extension from the file name string.
let nameLength = file.length;
let dotLastIndex = file.lastIndexOf('.');
let finalName = file.substring(0, dotLastIndex);
In the above syntax, we first use the length property to get the length of the file name. After that, we find the last index of the point and then use the substring() method to get the substring before the last point.
Example 3
In the example below, when the user uploads any file, the input will trigger the onchange event and call the removeExtension() javascript function. In the function, we use lastIndexOf() method and substring() method to remove the file extension from the file name of the uploaded file.
<html>
<body>
<h2>Using the <i> substring() and lastIndexOf() </i> methods to remove the file extension from the string in JavaScript </h2>
<div id = "output"></div>
<input type = "file" name = "file" onchange = "removeExtension(this)">
<br>
<script>
let output = document.getElementById("output");
function removeExtension(event) {
let file = event.files[0].name;
output.innerHTML += "The original file name is " + file + "<br/>";
let nameLength = file.length;
let dotLastIndex = file.lastIndexOf('.');
let finalName = file.substring(0, dotLastIndex);
output.innerHTML += "The final file name after trimming the extension is " + finalName + "<br/>";
}
</script>
</body>
</html>
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